Stocks opened flat Wednesday morning, with investors remaining cautious after the S&P 500 closed at a record high on Tuesday.
The Dow Jones Industrial Average was up 25 points, or 0.1 percent, in early trading, and the S&P 500 rose 5 points, or 0.2 percent.
On Tuesday, the S&P 500 erased all its losses from the coronavirus pandemic, breaking a record it set in February.
The swift recovery in equity markets, which lost about one-third of their value in March, has raised questions as to whether low interest rates and other extraordinary measures from the Federal Reserve have inflated a stock bubble.
The ratio of stock prices to their earnings is hovering at levels not seen since the 1990s, when the dot-com bubble famously crashed.